ABSTRACT
Summary More than 1 million ha of muck soil suitable for agriculture exists in the northern portion of the Corn Belt in the U.S.A. Corn (Zea mays L.) and soybeans (Glycine max [L.] Merrill) are the major grain crops grown on these soils. Because of problems associated with producing grain crops (e.g., wet conditions, early frosts, excessive weed competition), many farmers are using these muck soils for pasture. Since very little information is available on the fertility requirements of the pastures, a 2-year study was initiated in the spring of 1979 on Edwards muck soil (Limnic Medisaprist) on the Pinney-Purdue Agricultural Center at Wanatah in northwestern Indiana. Eight combinations of nitrogen (N)-phosphorus (P)-potassium (K) fertilizer were applied with 3 replications to a permanent Kentucky bluegrass (Poa pratensis L.) pasture. Dry-matter yield, percentage of crude protein, and mineral composition were determined for each of four cuttings taken during the 1979 and 1980 growing seasons. The harvested forage was from a 1.5-m2 cage randomly located in each replication. Application of N fertilizer had a pronounced effect, but P and K had little, if any, effect on dry-matter yield and crude-protein production over the 2-year period. The application of 168 kg/ha of N increased dry-matter yield of Kentucky bluegrass from 6.3 to 8.2 metric tons (mt)/ha in 1979 and from 6.4 to 7.8 mt/ha in 1980. Crude-protein production was increased from 1,153 to 1,983 kg/ha in 1979 and from 1,206 to 1,974 kg/ha in 1980. Nitrogen signficantly increased N concentration in plants, especially during the earlier part of the growing season. A slight increase in P concentration resulted from the application of P fertilizer; adequate levels of P were present, however, in control forages. Potassium levels in the plants increased with application of K fertilizer, but, again, K levels were adequate in plant tissue from the unfertilized treatment. Although P appeared to be adequate, the application of P with N increased the concentration of N over that of N fertilizer alone. The addition of N fertilizer resulted in a small, but highly significant, increase in K concentration.
